Conventional screen presses print multi-colored images on material by mounting the material to a pallet or platen and rotating the platen to each of a plurality of printing stations located peripherally about a central support, wherein a different color is printed on the material at each of the printing stations. The images printed at the several printing stations, when superimposed one over the other on the material, produce the desired multi-colored work.
For volume production of multiple printed copies, a plurality of platens are provided which are mounted for rotation about a central support column. The plurality of platens each have respective workpieces mounted thereon which are printed upon and advanced from station to station. It is also necessary that the object being printed be moved quickly from station to station in a multiple station printing apparatus, and necessary that the registration of the object to be printed with each of a succession of printing screens be maintained.
A variety of means have been developed for adjusting the location and orientation of screens on a screen printing press to allow the images produced thereby to be in accurate registration with one another. A particularly advantageous screen alignment system is that disclosed in co-pending U.S. patent application Ser. No. 770,518 now U.S. Pat. No. 5,188,026 entitled "Pin Registration System For Screen Printers." Therein, a registration table and pins are employed to accurately align images on each of the plurality of screens with respect to their associated screen frames. Then, each of the screen frames is mounted in a respective printing head with the alignment of the screens and images thereon being retained by use of a calibration pallet and registration pins to position each of the plurality of screens at an equal distance from both one another as well as from the central support column. Thus, by employing the "Pin Registration System For Screen Printers," the press will print each of the images of the various screens at the same orientation and spacing from the central support column, and therefore in accurate registration with one another.
When printing a number of objects such as T-shirts with the printed image being located generally centrally on the T-shirt, the platens holding the T-shirt are only generally located relative to the image on the printing screen. If the printed image is slightly off-center, the viewer will not usually notice that the printed image is off-center. However, it is often desirable to print "all over" or "to the edge" on a T-shirt, i.e., the image extending from one edge all across the T-shirt to the opposite edge, particularly across the arms of a T-shirt and to exactly the side edges of the T-shirt. In such case, the platens are carefully centered with respect to the image on the screen so that the printed image is centered on the T-shirt and does not leave an edge unprinted with printing being run off the other edge. An unprinted edge on a sleeve or along the body portion of a T-shirt, which is supposed to be printed completely across from one edge to the opposite edge, may result in the T-shirt becoming scrap. The alignment of the screens and the centered alignment of the platens relative to the images on the screens initially requires some skill on the part of the operator. A specialized platen or pallet for printing all over to the edges and onto the sleeves is disclosed in U.S. patent application Ser. No. 746,652, entitled "Shirt Pallet With Retractable Arms" which is hereby incorporated by reference as if fully reproduced herein.
Often, it is desired to make short runs, for example, printing a first run of T-shirts printed all over, followed by printing of a second run of other textiles using other screens and pallets, and then printing a third run of printed all over T-shirts using different colors but using the same images previously printed during the first run. Using conventional screen printing equipment, it would be necessary for a skilled person to register all of the printing screens, and then to adjust laboriously again the platens on their support arms to center again all of the platens beneath the respective screens to assure that the printing extends from edge to edge and is centered on the T-shirts without leaving one edge bare and unprinted. Such set-up time and the use of skilled labor to do the re-registration of the pallets and screens is time-consuming and costly.
Thus, there is a need for a system of reducing the set-up time associated with accurately remounting material-supporting pallets and/or screens in their previously registered positions relative to one another.